As is well known, cellphones communicate by radiolink with an infrastructure of base stations positioned at locations distributed around the geographical area within which the cellphone network operates.
When a cell phone is first powered up, or when it moves from one cell to another, it has to search for a base station. The current, or power, which the modem of the cell phone uses whilst searching for a base station is greater than that used after it has logged itself on to a base station. The battery that is used therefore has to be sufficiently highly rated to provide for the higher level of power or current which is needed during the searching process. As a result, the physical size of the battery must be sufficiently great to enable the battery to deliver the required higher levels of power or current and to have a sufficiently long life (i.e. time between rechargings) to enable it to be practical.